The Edison light bulb, i.e. the incandescent bulb, and socket have been around for over 100 years virtually unchanged as a testament to Edison's design. It incorporates a glass envelope, or bulb, with a closed volume and a glass fuse enclosure extending therein. Connecting wires run in the glass fuse enclosure and extend outward into the closed volume of the glass envelope. A coiled tungsten filament runs between the connecting wires and is supported by the supporting wires. The filament in a light bulb is made of a long, incredibly thin length of tungsten metal. In a typical 60-watt bulb, the tungsten filament is over 6 feet long but only one-hundredth of an inch thick. The tungsten is arranged in a double coil in order to fit it all in a small space. That is, the filament is wound up to make one coil, and then this coil is wound to make a larger coil. In a 60-watt bulb, the coil is less than an inch long.
The glass envelope is filled with an inert gas or gases at a low pressure. A screw cap caps the glass envelope at its base to create the closed volume. The glass fuse enclosure and the connecting wires are secured to the screw cap with one connecting wire in contact with the electrical foot contact in the screw cap and the other connecting wire in contact with the side of the screw cap. The glass fuse enclosure and the screw cap can be filled with an insulating material to isolate the connecting wires from each other.
When the bulb is connected to a power supply, an electric current flows from one contact to the other, through the wires and the filament. Electric current in a solid conductor is the mass movement of free electrons from a negatively charged area to a positively charged area.
As the electrons zip along through the filament, they are constantly bumping into the atoms that make up the filament. The energy of each impact vibrates an atom. In other words, the current heats the atoms up. A thinner conductor heats up more easily than a thicker conductor because it is more resistant to the movement of electrons.
Bound electrons in the vibrating atoms may be boosted temporarily to a higher energy level. When they fall back to their normal levels, the electrons release the extra energy in the form of photons. Metal atoms release mostly infrared light photons, which are invisible to the human eye. But if they are heated to a high enough level—around 4,000 degrees Fahrenheit (2,200 degrees Celsius) in the case of a light bulb—they will emit a good amount of visible light.
While the incandescent light bulb is good at creating visible light as demonstrated by its longevity over the years, it is very inefficient as can be gleaned by the process described above in creating light and uses a large amount of energy relative to its visible light output. As resources used to create energy have become more scarce and concerns about environment impact by consumption of such resources have grown, society has begun to look for a satisfactory replacement for the incandescent light bulb that is more energy efficient but still provides the desired amount of visible light.
Standards have been developed to begin to require the use of high efficiency lighting also known as high efficacy lighting. For example, the State of California has enacted energy efficiency standards for residential and nonresidential buildings, known as Title 24-2005 (hereinafter refer to as “California Title 24”). California estimates its efficiency standards will save $43 billion by 2013. Stricter efficiency standards also help avoid rolling blackouts, reduce peak demand, and avoid the need to build new generating capacity. California Title 24 requires high efficacy lighting, occupancy sensors or dimmers in almost all spaces. In general, high-efficacy lighting is generally thought of as energy-efficient lighting fixtures. Fluorescent and compact fluorescent (CFL) fixtures with electronic ballasts, as well as certain high-intensity discharge (HID) lamps fall into this category. Also, lighting fixtures that employ light emitting diodes (hereinafter “LED”) are also considered high efficacy. Fluorescent and CFL fixtures with magnetic ballasts, incandescent lights and fixtures with incandescent sockets (regardless of the bulb type installed) are not considered high efficacy. Under California Title 24, high-efficacy lighting is defined as:                15 watts or less: Minimum of 40 lumens/watt;        15 to 40 watts: Minimum of 50 lumens/watt; and        More than 40 watts: Minimum of 60 lumens/watt.        
To ensure that only proper high efficacy lighting devices will be used in the high efficacy lighting systems, a new engagement arrangement for securing the high efficacy lighting devices in, for example, a high efficacy lighting ballast was developed that does not work with the traditional incandescent lamp/bulb engagement arrangement. The traditional incandescent lamp/bulb engagement arrangement is the screw cap and socket arrangement. The screw cap, which has helical threads on its sidewalls and a foot contact at its base, screws into the socket which has matching threaded sidewalls and an electrical contact.
The GU-24 socket and base system is designed to replace the Edison socket and base in energy efficient lighting fixtures. These bases differ from traditional screw-in sockets in that they offer a simpler twist-and-click method of installation or removal. GU-24 lighting devices have two pins in the base which connect to the socket with a twist-and-lock connection. The two pins of the GU-24 lighting devices are inserted into socket holes in the socket. Once inserted, the lighting devices can be rotated, or twisted, in a clockwise direction in a 1/8, a 1/4 or a 1/2 of a turn to lock the base of the lighting devices in place in the socket. Screw-in CFLs and incandescent bulbs cannot be used in GU-24 fixtures.
The ENERGY STAR® Program Requirements for Residential Lighting Fixtures, Version 4.0 require that residential lighting fixtures cannot use the standard Edison screw base, even if they do not have a built-in ballast. The same requirement is comprised in California Title 24. This requirement is designed to insure that fixtures that receive ENERGY STAR® qualification when using an energy-efficient self-ballasted CFL, or are qualified as energy-efficient under California Title 24, cannot be operated with an incandescent lamp.
Beginning August 2008, the ENERGY STAR® technical specification (v4.1) expanded to comprise lamps that work with GU-24 bases. The major benefit of this new interface is that any fixture with a GU-24 socket will work with any bulb having a GU-24 connection.
Thus, the GU-24 socket was designed to be compatible with these energy efficiency regulations. The GU-24 base has two dual-diameter pins; the smaller portion having a diameter of 3.4 mm (0.13 inches) while the larger portion has a diameter of 5 mm (0.2 inches). Lighting devices with a GU-24 base are designed to be connected directly to the power line, so they are functionally equivalent to screw-base lighting devices instead of normal pin-base CFLs.
Another advantage of the GU-24 standard is that the lamp and ballast are always housed in the same unit. While slightly more costly to produce, this is more than overcome by their increased convenience and simplicity of maintenance. The savings become even more pronounced where lighting requirements are greater and more stringent, such as in large commercial facilities.
While the GU-24 socket and base system provide a good sturdy for lighting devices that hang downward to extend upward in a direction axial with the force of gravity, this does not hold true for every orientation of a lighting device using such a system. For example, the GU-24 socket and base system provides a less sturdy connection when the lighting device is held at an angle. For instance, the use of the GU-24 socket and base system in track lighting can be dangerous due to the fact that the lighting devices can be adjusted to and often are in an angled position. Since the lighting device is only twisted in a partial turn, it can have the tendency to “untwist if held at the right angle. This could lead to an electrical disconnection of the lighting device or even the disengagement the lighting device from the socket. Such disengagement of the lighting device from the socket can easily lead to property damage and/or personal injury.